Laminated body and method for producing the same

Abstract

To provide a laminated body in which an anchor layer is provided between a resin layer containing a poly(3-hydroxyalkanoate) resin and a paper base layer, the laminated body having good adhesion between the resin layer and the paper base layer while using, in the anchor layer, a resin having a high glass transition temperature.SOLUTION: A laminated body comprises, stacked in the stated order, a paper base layer, an anchor layer containing a polyester resin (A) having a glass transition temperature exceeding 46°C and an acid value of 30 mgKOH / g or more, and a resin layer containing a poly(3-hydroxyalkanoate) resin (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate in which a resin layer containing a poly(3-hydroxyalkanoate) resin is laminated on a paper substrate layer, and to a method for producing the same. [Background technology]

[0002] In recent years, environmental problems caused by discarded plastics have been attracting attention. In particular, marine pollution caused by discarded plastics is serious, and there are high hopes for the widespread use of biodegradable plastics that decompose in the natural environment.

[0003] Poly(3-hydroxyalkanoate) resins are thermoplastic polyesters that are produced and accumulated as energy storage substances within the cells of many microbial species. They are also biodegradable not only in soil but also in seawater, and are therefore attracting attention as a material that can solve the above problems.

[0004] A laminate formed by laminating a resin layer whose main component is such a poly(3-hydroxyalkanoate)-based resin onto a biodegradable paper substrate is extremely promising from the perspective of environmental protection, since both the resin and the substrate are materials with excellent biodegradability.

[0005] In order to improve the adhesion between the resin layer and the paper base layer in such a laminate, Patent Document 1 describes providing a coating layer containing a polyester resin with a glass transition temperature of -25 to 46°C as an anchor layer between the resin layer and the paper base layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7285387 Summary of the Invention [Problem to be solved by the invention]

[0007] According to the method described in Patent Document 1, it is possible to improve the adhesion between a resin layer containing a poly(3-hydroxyalkanoate) resin as a main component and a paper substrate layer. In the invention described in this document, the glass transition temperature of the polyester resin used in the anchor layer is limited to 46° C. or less. It has been shown that when a polyester resin with a glass transition temperature exceeding 46° C. is used, adhesion is not improved (see Comparative Examples 1 to 4 in this document).

[0008] However, the laminate including the paper base layer and the resin layer is expected to be used for packaging or storing hot food and drink, etc., and heat resistance is required for such applications. In order to improve the heat resistance of the laminate, it is desirable to use a resin constituting the anchor layer that has as high a glass transition temperature as possible.

[0009] In view of the above-mentioned current situation, the present invention aims to provide a laminate in which an anchor layer is provided between a resin layer containing a poly(3-hydroxyalkanoate)-based resin and a paper base layer, and in which a resin with a high glass transition temperature is used in the anchor layer while the resin layer and the paper base layer have good adhesion. [Means for solving the problem]

[0010] As a result of intensive research to solve the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by selecting and using, as the resin constituting the anchor layer, a polyester-based resin that exhibits a high acid value even if its glass transition temperature exceeds 46°C, and have thereby completed the present invention.

[0011] That is, the present invention provides a paper substrate layer, An anchor layer containing a polyester resin (A) having a glass transition temperature of more than 46°C and an acid value of 30 mgKOH / g or more; and The present invention relates to a laminate comprising a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B), and each layer being laminated in this order. The present invention also provides a method for producing a paper substrate, comprising the steps of: (i) applying an aqueous liquid (I) containing a polyester resin (A) having a glass transition temperature of more than 46°C and an acid value of 30 mgKOH / g or more to the surface of the paper substrate and drying the liquid to form an anchor layer; The present invention also relates to a method for producing a laminate, which includes a step (ii) of forming a resin layer containing a poly(3-hydroxyalkanoate) resin (B) on the surface of the anchor layer. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a laminate having an anchor layer between a resin layer containing a poly(3-hydroxyalkanoate) resin and a paper base layer, in which the anchor layer uses a resin with a high glass transition temperature, and yet the adhesiveness between the resin layer and the paper base layer is good. Because the anchor layer uses a resin with a high glass transition temperature, the heat resistance of the laminate can be improved. According to a preferred embodiment of the present invention, a laminate having good adhesion and good oil resistance can be provided. When the laminate is used as a packaging material for packaging oily foods, for example, the seepage of oil can be suppressed. Furthermore, according to a preferred embodiment of the present invention, the biodegradability of the entire laminate can be improved. Furthermore, according to a preferred embodiment of the present invention, the laminate can be produced with good productivity. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0014] [Laminate] A laminate according to one embodiment of the present invention has an anchor layer and a resin layer containing a poly(3-hydroxyalkanoate) resin (B) on at least one side of a paper substrate layer, the paper substrate layer, the anchor layer, and the resin layer being laminated in this order.

[0015] The anchor layer may be laminated directly on the paper base layer, or another layer may be further included between the anchor layer and the paper base layer as long as it does not impair adhesion.

[0016] The resin layer may be the outermost layer in the laminate, and in this case, the resin layer may function as a heat seal layer, a water-resistant layer, and / or an oil-resistant layer.

[0017] Furthermore, another layer may be laminated on the resin layer. The other layer is not particularly limited, and may be another resin layer or an inorganic layer.

[0018] The laminate may have the anchor layer and the resin layer on only one side of the paper base layer, or may have the anchor layer and the resin layer on each side of the paper base layer. When the paper substrate layer has an anchor layer and a resin layer on only one side, the other side of the paper substrate layer may be exposed without any other layer laminated thereon. Alternatively, for the purpose of imparting water resistance, glossiness, or adhesiveness, another layer may be laminated on the other side of the paper substrate layer.

[0019] When the paper base layer has an anchor layer and a resin layer on each side, the materials constituting the anchor layer on the front side and the anchor layer on the back side, as well as the basis weight and thickness, may be the same or different. The same applies to the resin layer on the front side and the resin layer on the back side. The basis weight refers to the dry weight (solid content) of the layer.

[0020] [Paper base layer] The paper base layer is composed of a sheet mainly made of pulp, and can be obtained by papermaking a stock containing pulp, fillers, various auxiliaries, etc. The type of paper that can be used is not particularly limited, and examples include cup base paper, kraft paper, fine paper, coated paper, tissue paper, glassine paper, and paperboard.

[0021] The pulp is not particularly limited, and examples thereof include chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), and sulfite pulp; mechanical pulps such as stone-ground pulp and thermomechanical pulp; wood fibers such as deinked pulp and recycled paper pulp; and non-wood fibers obtained from kenaf, bamboo, hemp, etc. These can be used in appropriate combinations.

[0022] Among these, it is preferable to use chemical pulp or mechanical pulp made from wood fibers, and it is more preferable to use chemical pulp, for reasons such as the paper being less likely to be contaminated with foreign matter, being less likely to discolor over time when recycled as waste paper raw material, and having a high degree of whiteness, which results in a good surface appearance when printed, and which is particularly valuable when used as a packaging material. Specifically, it is preferable that the amount of chemical pulp such as LBKP or NBKP in the pulp is 80% or more, and it is particularly preferable that the amount of chemical pulp is 100%.

[0023] The filler is not particularly limited, and examples thereof include inorganic fillers such as talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, and calcium sulfate; and organic fillers such as urea-formalin resin, polystyrene resin, phenolic resin, and hollow microparticles. Note that fillers are not essential materials and may not be used.

[0024] The various auxiliaries are not particularly limited and include, for example, sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA), polyacrylamide polymers, polyvinyl alcohol polymers, cationized starch, various modified starches, dry strength agents such as urea-formalin resin and melamine-formalin resin, wet strength agents, retention aids, drainage aids, coagulants, aluminum sulfate, bulking agents, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, UV inhibitors, anti-fading agents, pitch control agents, slime control agents, etc. These may be selected and used as needed.

[0025] The surface of the paper may be treated with various chemicals. The chemicals are not particularly limited, and examples thereof include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water-retaining agents, thickeners, and lubricants. Only one type of chemical may be used, or two or more types may be used in combination. Furthermore, these chemicals may be used in combination with pigments.

[0026] The pigment is not particularly limited, and examples thereof include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white; and organic pigments such as solid, hollow, and core-shell pigments. Only one type of pigment may be used, or two or more types may be used in combination.

[0027] The basis weight of the paper substrate can be selected appropriately depending on the desired quality and the use of the laminate, but is preferably 40 g / m 2 More than 400g / m 2 Preferably, it is 50 g / m or less. 2 More than 350g / m 2 When the laminate is used for packaging materials such as wrapping paper, paper bags, lids, liner papers, and soft packaging materials, or posters to be used outdoors, the weight is more preferably 40 g / m 2 More than 150g / m 2It is more preferable that the soft packaging material is a packaging material having a density of 40 g / m or less. 2 ~100g / m 2 It refers to a flexible packaging material made of thin paper of about 150 g / m². When the laminate is used for paper tableware such as paper cups, paper boxes, paper plates, paper trays, etc., or for lids and other paper containers, it is recommended that the thickness be 150 g / m². 2 More than 400g / m 2 It is more preferable that:

[0028] The density of the paper substrate can be selected appropriately depending on the desired quality, handling, etc., but is usually 0.5 g / cm 3 More than 1.0g / cm 3 It is preferable that:

[0029] The method for producing the paper base (papermaking) is not particularly limited, and can be carried out by appropriately selecting a known papermaking machine, such as a Fourdrinier papermaking machine, a cylinder papermaking machine, a short wire papermaking machine, or a twin-wire papermaking machine such as a gap former type or a hybrid former type (on-top former type). The pH during papermaking may be in the acidic range (acidic papermaking), pseudo-neutral range (pseudo-neutral papermaking), neutral range (neutral papermaking), or alkaline range (alkaline papermaking). After papermaking in the acidic range, an alkaline agent may be applied to the surface of the paper layer. The paper base may be composed of a single layer, or two or more layers.

[0030] When treating the surface of a paper substrate with a chemical, the method of surface treatment is not particularly limited, and known coating devices such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, or a curtain coater can be used.

[0031] Anchor layer The anchor layer is a layer composed mainly of a polyester resin (A). By providing such an anchor layer between the paper substrate layer and the resin layer, the adhesion between the resin layer and the paper substrate layer can be improved. Furthermore, when the laminate according to this embodiment is bonded by heat sealing, the adhesive strength can be improved. Furthermore, by providing an anchor layer in addition to the resin layer, the oil resistance of the laminate is improved, and when it comes into contact with oily foods, etc., the seepage of oil can be suppressed.

[0032] The polyester resin (A) used has a glass transition temperature (hereinafter also referred to as Tg) of more than 46° C. This improves the heat resistance of the anchor layer, making it possible to prevent the anchor layer from losing its functionality even when the laminate is exposed to high temperatures.

[0033] The Tg of the polyester resin (A) is not particularly limited as long as it is a temperature above 46° C., but is preferably 47° C. or higher, and more preferably 49° C. or higher. There is no particular upper limit to the Tg, but from the viewpoint of improving the adhesion between the resin layer and the paper substrate layer, it is preferably 90° C. or lower, more preferably 70° C. or lower, even more preferably 60° C. or lower, and particularly preferably 55° C. or lower.

[0034] The Tg of the polyester resin (A) can be controlled by adjusting the types and the ratio of the monomers constituting the polyester resin. The Tg of the polyester resin (A) can be measured by differential thermal analysis.

[0035] The polyester resin (A) has a Tg of over 46°C and an acid value of 30 mgKOH / g or more. By using a polyester resin (A) with a high acid value of 30 mgKOH / g or more in the anchor layer, it is possible to improve the adhesion between the resin layer and the paper base layer and the heat-seal adhesive strength. If a polyester resin with a high Tg of over 46°C and a low acid value of less than 30 mgKOH / g is used, the adhesion will be insufficient.

[0036] It is presumed that the use of a polyester resin with a high acid value improves the affinity between the anchor layer and the paper base layer, thereby improving the adhesion between the anchor layer and the paper base layer.

[0037] The acid value of a polyester resin is a value attributable to acidic groups such as carboxyl groups contained in the polyester resin, and the greater the content of acidic groups, the higher the acid value. Specifically, the acid value of a polyester resin is expressed as the mass (mg) of potassium hydroxide required to neutralize 1 g of polyester resin.

[0038] The lower limit of the acid value of the polyester resin (A) is not particularly limited as long as it is 30 mgKOH / g or more, but from the viewpoint of the influence on the adhesion between the resin layer and the paper base layer and the adhesive strength of the heat seal, it is preferably 40 mgKOH / g or more, more preferably 45 mgKOH / g or more, and particularly preferably 50 mgKOH / g or more.

[0039] The upper limit of the acid value of the polyester resin (A) is not particularly limited, but from the viewpoint of the productivity of the resin and the effect on the physical properties of the laminate, it is preferably 120 mgKOH / g or less, more preferably 100 mgKOH / g or less, and particularly preferably 80 mgKOH / g or less.

[0040] The polyester resin (A) is preferably biodegradable, which means that the resins constituting the paper substrate layer and the resin layer are both biodegradable, and the resin material constituting the anchor layer is also biodegradable, thereby enhancing the biodegradability of the entire laminate.

[0041] In this application, the term "biodegradable polyester resin" refers to a polyester resin whose biodegradability reaches 40% or more after a test period of 60 days when the biodegradability of the polyester resin is determined in accordance with "Plastics - Determination of ultimate aerobic biodegradability under controlled compost conditions - Method by measuring the amount of carbon dioxide generated" specified in JIS K6953-2.

[0042] Specific types of polyester-based resin (A) include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN); aliphatic polyester-based resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid; and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate.

[0043] The polyester resin (A) is preferably a polyester resin formed by polycondensation of a polyalcohol component and a polycarboxylic acid component, and is particularly preferably a polyester resin formed by dehydration condensation of a diol component, a dicarboxylic acid component, and a tricarboxylic or higher polycarboxylic acid. By using a tricarboxylic or higher polycarboxylic acid, the polyester resin (A) can exhibit a high acid value.

[0044] Examples of the diol component include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol; aromatic diols such as 1,4-benzenedimethanol and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene; and ether group-containing diols such as diethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

[0045] The diol component may also be a branched diol component, specific examples of which include neopentyl glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,2-hexanediol, 2,5-hexanediol, and 2,4-diethyl-1,5-pentanediol. The diol component may be used alone or in combination of two or more kinds.

[0046] Trihydric or higher alcohol components may be used in combination with the diol component, and specific examples thereof include triol compounds such as aliphatic triols such as glycerin and trimethylolpropane, alicyclic triols such as 1,2,4-cyclohexanetrimethanol, aromatic triols such as benzenetrimethanol, and tetraol compounds such as pentaerythritol.

[0047] Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 2,5-furandicarboxylic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; and aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedioic acid, as well as dicarboxylic acids, esters thereof, and anhydrides thereof. Only one of these may be used, or two or more may be used in combination.

[0048] Examples of the trivalent or higher polycarboxylic acids include hemimellitic acid, trimellitic acid, trimesic acid, mellophanic acid, pyromellitic acid, benzenepentacarboxylic acid, mellitic acid, cyclopropane-1,2,3-tricarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid, and ethanetetracarboxylic acid. Esters or anhydrides of these may also be used. These may be used alone or in combination of two or more.

[0049] As the dicarboxylic acid component and the polycarboxylic acid component containing the trivalent or higher polycarboxylic acid, a metal sulfonate group-containing polycarboxylic acid is preferably used to impart good water solubility to the polyester resin. Specific examples include alkali metal salts of 5-sulfoisophthalic acid, alkali metal salts of 2-sulfoisophthalic acid, alkali metal salts of 4-sulfoisophthalic acid, alkali metal salts of sulfoterephthalic acid, and alkali metal salts of 4-sulfonaphthalene-2,6-dicarboxylic acid. The metal in the metal sulfonate group-containing polycarboxylic acid is preferably sodium, potassium, or lithium.

[0050] The proportion of the metal sulfonate group-containing polycarboxylic acid relative to the entire polycarboxylic acid component is preferably within a range of 1 to 30 mol %, more preferably within a range of 5 to 20 mol %.

[0051] As the polyester resin (A) satisfying the above-mentioned requirements for Tg and acid value, commercially available products may be used. Examples of such commercially available products include water-soluble polyester PLAS COAT series Z-760, GX-1484, GX-1488, GX-1489, GX-1448, and GX-1473 (all manufactured by GOO Chemical Industry Co., Ltd.). Among these, GX-1473 is preferred because of its biodegradability.

[0052] The resin component contained in the anchor layer may be polyester resin (A) alone, or may contain a poly(3-hydroxyalkanoate) resin (C) together with the polyester resin (A). By including poly(3-hydroxyalkanoate) resin (C) in the anchor layer, it is possible to increase the affinity between the anchor layer and the resin layer, and further increase the adhesion between the resin layer and the paper substrate layer and the heat-seal adhesive strength.

[0053] The definition and specific examples of the poly(3-hydroxyalkanoate) resin (C) are the same as those of the poly(3-hydroxyalkanoate) resin (B) described later, and therefore will not be described here. In particular, it is preferable to use a poly(3-hydroxybutyrate) copolymer (c-2) containing 3-hydroxybutyrate units and other hydroxyalkanoate units as the poly(3-hydroxyalkanoate) resin (C). This copolymer may also be used in combination with poly(3-hydroxybutyrate) (c-1). Details of poly(3-hydroxybutyrate) (c-1) and copolymer (c-2) are the same as those of poly(3-hydroxybutyrate) (b-1) and copolymer (b-2) described below, and therefore will not be repeated here.

[0054] The content of the poly(3-hydroxyalkanoate) resin (C) in the anchor layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and even more preferably 3% by weight or more, as a ratio of the resin (C) to the total of the polyester resin (A) and the resin (C). On the other hand, from the viewpoint of suppressing the heating temperature when forming the anchor layer, the upper limit of the ratio is preferably 50% by weight or less, more preferably 30% by weight or less, and even more preferably 20% by weight or less.

[0055] The proportion of the polyester resin (A) contained in the anchor layer, or the combined proportion of the polyester resin (A) and the poly(3-hydroxyalkanoate) resin (C), is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more, of the total amount (solid content) of the anchor layer. The upper limit may be 100% by weight or less, and may be 99% by weight or less.

[0056] Components in the anchor layer other than the polyester resin (A) and the poly(3-hydroxyalkanoate) resin (C) include other resins (particularly water-soluble resins or water-dispersible resins), dispersants, viscosity improvers, water retention agents, antifoaming agents, water-resistant agents, pH adjusters, cationic resins, anionic resins, ultraviolet absorbers, metal salts, lubricants, coloring dyes, pigments, etc.

[0057] As described below, the anchor layer is preferably a coated layer of a coating agent, and particularly preferably a coated layer of a water-dispersible coating agent, which allows the anchor layer to be formed simply by applying the water-dispersible coating agent and then performing a heat treatment to evaporate the water, thereby improving the productivity of the laminate.

[0058] The basis weight of the anchor layer is not particularly limited, but is, for example, 0.1 g / m in dry weight. 2 More than 10g / m 2 The lower limit is 0.5 g / m because the adhesion and oil resistance are improved. 2 It is preferable that the content is 1 g / m or more. 2 More preferably, 3 g / m 2 More preferably, 4 g / m 2 The upper limit is 8 g / m because it is possible to reduce the energy required for the drying process required for forming the anchor layer. 2 More preferably, it is 6 g / m or less. 2 The following is even more preferred:

[0059] [Resin layer] The resin layer contains a poly(3-hydroxyalkanoate)-based resin (B) (hereinafter also referred to as "P3HA-based resin (B)"). The resin layer may be the outermost layer in the laminate according to this embodiment. In this case, the resin layer can be used for heat sealing (described below).

[0060] The P3HA resin is a biodegradable aliphatic polyester (preferably a polyester containing no aromatic ring), and is a polymer having at least one or more types of 3-hydroxyalkanoate units. The 3-hydroxyalkanoate units are preferably represented by the following general formula (1): [-CHR-CH2-CO-O-] (1)

[0061] In the general formula (1), R is C p H 2p+1where p is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. p is preferably 1 to 10, and more preferably 1 to 8.

[0062] The P3HA resin preferably contains 3-hydroxyalkanoate units (particularly units represented by general formula (1)) in an amount of 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more of the total structural units (monomer units). The poly(3-hydroxyalkanoate) resin may contain only one or more types of 3-hydroxyalkanoate units as structural units of the polymer, or may contain one or more types of 3-hydroxyalkanoate units as well as other units (e.g., 4-hydroxyalkanoate units).

[0063] The content of the P3HA-based resin (B) in the resin layer is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more of the total amount (solid content) of the resin layer. By using the P3HA-based resin as a main component, the resin layer can exhibit good biodegradability.

[0064] The P3HA resin is preferably a poly(3-hydroxybutyrate) resin (hereinafter also referred to as a P3HB resin). The P3HB resin contains poly(3-hydroxybutyrate) (b-1) and / or poly(3-hydroxybutyrate) copolymer (b-2) containing 3-hydroxybutyrate units and other hydroxyalkanoate units. From the viewpoint of seawater degradability, it is preferable to contain poly(3-hydroxybutyrate) copolymer (b-2).

[0065] The type of copolymerization in the copolymer is not particularly limited, and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc. Copolymers produced by microorganisms are usually random copolymers.

[0066] The hydroxyalkanoic acid that forms the other hydroxyalkanoate unit is not particularly limited, and examples thereof include 4-hydroxybutanoic acid, 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, and 3-hydroxyoctanoic acid.

[0067] Specific examples of the poly(3-hydroxybutyrate) copolymer (b-2) include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxybutyrate) (abbreviation: P3HB4HB), Examples of copolymers include poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviation: P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH). Among these, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because of their ease of industrial production. As copolymer (b-2), one type may be used alone, or two or more types may be used in combination.

[0068] Among P3HB-based resins, P3HB3HH is particularly preferred from the viewpoints that its melting point and degree of crystallinity can be altered by changing the composition ratio of the repeating units, thereby enabling adjustment of physical properties such as Young's modulus and heat resistance, and that it can be given physical properties intermediate between those of polypropylene and polyethylene. It is also easy to produce industrially and is a physically useful plastic.

[0069] The content of the P3HB resin in the resin layer is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more of the total amount (solid content) of the resin layer. By using a P3HB resin as a main component, the resin layer can exhibit good biodegradability.

[0070] The resin layer preferably contains poly(3-hydroxybutyrate) (b-1) (hereinafter also referred to as PHB (b-1)) as the P3HA-based resin (B). By including PHB (b-1), the P3HA-based resin (B) is rapidly solidified after melting in the heating step, thereby improving the productivity of the laminate.

[0071] PHB(b-1) refers to a homopolymer composed only of 3-hydroxybutyrate, or a polymer containing a trace amount of hydroxyalkanoate units other than 3-hydroxybutyrate units in addition to 3-hydroxybutyrate units. Specifically, PHB(b-1) preferably contains 3-hydroxybutyrate units in a proportion of more than 99 mol% and not more than 100 mol% of all of its constituent monomers.

[0072] The hydroxyalkanoate units other than 3-hydroxybutyrate units that can be contained in PHB (b-1) are not particularly limited as long as they are copolymerizable with 3-hydroxybutyrate units, and examples thereof include 3-hydroxyalkanoate units other than 3-hydroxybutyrate units and hydroxyalkanoate units other than 3-hydroxyalkanoate units (e.g., 4-hydroxyalkanoate units). In particular, 3-hydroxyhexanoate units are preferred.

[0073] The weight average molecular weight of PHB (b-1) is not particularly limited, but from the viewpoints of the productivity of the laminate, the water resistance and oil resistance of the resin layer, and the mechanical properties of the resin layer, it is preferably 100,000 or more and less than 400,000, and more preferably 200,000 or more and 350,000 or less.

[0074] The weight-average molecular weight (hereinafter, sometimes referred to as Mw) of PHB (b-1) can be determined as the molecular weight converted into polystyrene by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) using a polystyrene gel (Shodex K-804 manufactured by Showa Denko K.K.) as a column and chloroform as a mobile phase.

[0075] The content of PHB (b-1) in the resin layer is preferably 12% by weight or more and 21% by weight or less, based on the total amount (100% by weight) of the P3HA resin (B), from the viewpoints of productivity of the laminate and water resistance and oil resistance of the resin layer. From the viewpoint of productivity of the laminate, the content is more preferably 13% by weight or more. From the viewpoint of oil resistance, the content is preferably 18% by weight or less, more preferably 16% by weight or less.

[0076] In addition to PHB (b-1), the resin layer preferably further contains a poly(3-hydroxybutyrate)-based copolymer (b-2) containing 3-hydroxybutyrate units and other hydroxyalkanoate units. The inclusion of copolymer (b-2) facilitates melting of the P3HA-based resin (B) during the heating process, facilitating homogenization of the resin layer by heating, thereby improving the water resistance and oil resistance of the laminate. However, the resin layer may also contain only copolymer (b-2) as the P3HA-based resin (B) without PHB (b-1).

[0077] Specific examples of the copolymer (b-2) include the copolymers mentioned above, and among them, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferred.

[0078] The content of the other hydroxyalkanoate units out of 100 mol% of the total monomer units constituting the poly(3-hydroxybutyrate) copolymer (b-2) is preferably 10 mol% or more and less than 24 mol%, more preferably 10 mol% or more and less than 20 mol%, and even more preferably 10 mol% or more and less than 18 mol%, from the viewpoint of achieving both meltability in the heating step and productivity of the resin.

[0079] The average content of the other hydroxyalkanoate units out of 100 mol% of all monomer units contained in the entire P3HA-based resin (B) contained in the resin layer is preferably 5 mol% or more and 18 mol% or less, more preferably 6 mol% or more and 16 mol% or less, even more preferably 7 mol% or more and 14 mol% or less, and particularly preferably 8 mol% or more and 12 mol% or less, from the viewpoint of achieving both meltability in the heating step and productivity of the resin.

[0080] The average content ratio of each monomer unit relative to 100 mol% of all monomer units contained in the entire P3HA-based resin (B) can be determined by a method known to those skilled in the art, for example, the method described in paragraph

[0047] of WO 2013 / 147139. When the P3HA-based resin (B) is a mixture of two or more resins, the average content ratio refers to the average molar ratio of each monomer unit relative to 100 mol% of all monomer units contained in the entire mixture.

[0081] The weight-average molecular weight of the poly(3-hydroxybutyrate) copolymer (b-2) is not particularly limited, but is preferably 100,000 or more and less than 400,000, and more preferably 200,000 or more and 350,000 or less, from the viewpoints of the productivity of the laminate, the water resistance and oil resistance of the resin layer, the mechanical properties of the resin layer, etc. The weight-average molecular weight can be measured by the method described above.

[0082] A specific method for producing poly(3-hydroxybutyrate) copolymer (b-2) is described in, for example, WO 2010 / 013483. Commercially available PHBH products include Kaneka Biodegradable Polymer Green Planet (registered trademark) manufactured by Kaneka Corporation.

[0083] The weight-average molecular weight of the entire P3HA resin (B) is not particularly limited, but is preferably from 100,000 to less than 400,000, and more preferably from 200,000 to 350,000, from the viewpoints of the productivity of the laminate, the water resistance and oil resistance of the resin layer, and the mechanical properties of the resin layer, etc. The weight-average molecular weight can be measured by the method described above.

[0084] The resin layer may contain, to the extent that the effects of the invention are not impaired, one or more of the following: resins other than the P3HA-based resin (B), adhesives, dispersants or emulsifiers, pH adjusters, inorganic fillers, colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather resistance improvers, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding improvers. However, these are optional components, and the resin layer may not contain these components.

[0085] Resins other than the P3HA-based resin (B) that can be used in the resin layer are not particularly limited, but are preferably biodegradable resins. Specific examples include aliphatic polyester-based resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate. The blend amount of such other resins may be 50 parts by weight or less, 30 parts by weight or less, or 10 parts by weight or less, per 100 parts by weight of the P3HA-based resin (B). It may also be 5 parts by weight or less, or 1 part by weight or less.

[0086] The weight of the resin layer can be appropriately determined in consideration of the performance and productivity required of the resin layer. Specifically, the weight of the resin layer is 1.0 g / m2 in dry weight. 2 More than 80g / m 2 Preferably, it is 5.0 g / m or less. 2 More than 60g / m 2 Less than 10 g / m is more preferable. 2More than 50g / m 2 When the basis weight of the resin layer is within the above range, defects such as pinholes can be prevented, the resin layer can have a strength sufficient for use, and functions such as water resistance and oil resistance can be efficiently exhibited.

[0087] [Method for manufacturing laminate] An example of a method for producing the laminate according to this embodiment will be described below. The laminate according to this embodiment can be produced by sequentially carrying out step (i) of forming an anchor layer on at least one side of a paper substrate, and step (ii) of forming a resin layer containing a P3HA-based resin (B) on the surface of the formed anchor layer.

[0088] [Step (i): Formation of anchor layer] In step (i), the aqueous liquid (I) containing the polyester resin (A) described above is applied to one or both sides of the paper substrate and dried to form an anchor layer.

[0089] The aqueous liquid (I) containing the polyester resin (A) may be any liquid containing at least water and the polyester resin (A), and may be any of an aqueous solution or an aqueous dispersion such as an aqueous slurry or an aqueous emulsion. If necessary, components other than the polyester resin (A) may be dissolved or dispersed in the aqueous liquid (I).

[0090] The solvent contained in the aqueous liquid (I) may be water alone or a mixed solvent of water and an organic solvent. The organic solvent is preferably an organic solvent that is compatible with water. The concentration of the organic solvent is preferably equal to or less than the solubility of the organic solvent in water.

[0091] The solid content concentration of the polyester resin (A) in the aqueous liquid (I) is not particularly limited, but may be, for example, in the range of 10% by weight to 60% by weight.

[0092] The method for applying the aqueous liquid (I) to the paper substrate is not particularly limited, and any known method capable of forming a coating layer on the paper substrate can be used as appropriate. Specifically, methods such as spraying, scattering, slit coating, air knife coating, roll coating, bar coating, comma coating, blade coating, screen printing, and gravure printing can be used. Before applying the aqueous liquid (I), the paper substrate may be subjected to a surface treatment such as the above-mentioned corona treatment.

[0093] The drying treatment after coating can be carried out using a known heating method, such as hot air heating, infrared heating, microwave heating, roll heating, or hot plate heating, which can be used alone or in combination of two or more.

[0094] The heating temperature in the drying treatment is not particularly limited as long as it is a temperature at which water contained in the aqueous liquid (I) can be evaporated. Specifically, it is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. The upper limit may be less than 130°C and may be 125°C or lower. The heating time is not particularly limited, but may be, for example, 10 seconds to 10 minutes, and preferably about 30 seconds to 5 minutes.

[0095] [Step (ii): Formation of Resin Layer] Next, step (ii) is carried out to form a resin layer containing a P3HA-based resin (B) on the surface of the formed anchor layer. The resin layer may be formed by applying an aqueous dispersion (II) containing the P3HA resin (B) to the surface of the anchor layer and drying the applied dispersion to form the resin layer, or by laminating a resin composition containing the P3HA resin (B) on the surface of the anchor layer.

[0096] [Formation of resin layer by coating method] In the embodiment in which the resin layer is formed by applying an aqueous dispersion (II) containing a P3HA-based resin (B) to the surface of an anchor layer and drying it, first, the aqueous dispersion (II) is prepared. The aqueous dispersion (II) containing the P3HA resin (B) refers to a liquid in which at least resin particles containing the P3HA resin (B) are dispersed in water. The aqueous dispersion (II) may contain other components dissolved or dispersed therein, as necessary.

[0097] The aqueous dispersion (II) contains an aqueous solvent. The aqueous solvent may be water alone or a mixed solvent of water and an organic solvent. The organic solvent is preferably an organic solvent that is compatible with water. The concentration of the organic solvent is preferably equal to or less than the solubility of the organic solvent in water.

[0098] The solids concentration of the P3HA resin (B) in the aqueous dispersion (II) is not particularly limited, but is preferably 20% by weight or more and 60% by weight or less. When the solids concentration is within this range, the viscosity of the dispersion is not too high, allowing for uniform application, and the required coating thickness can be maintained, thereby preventing coating defects. The lower limit of the solids concentration is preferably 30% by weight or more, and more preferably 40% by weight or more.

[0099] The average particle size of the P3HA resin (B) in the aqueous dispersion (II) may be, for example, 0.1 to 50 μm, from the viewpoint of achieving both productivity of the P3HA resin (B) and uniformity during application.

[0100] The aqueous dispersion (II) may not contain an emulsifier, but preferably contains an emulsifier to stabilize the dispersion. Examples of emulsifiers include anionic surfactants such as sodium lauryl sulfate and sodium oleate, cationic surfactants such as lauryl trimethylammonium chloride, nonionic surfactants such as glycerin fatty acid esters and sorbitan fatty acid esters, polyvinyl alcohol derivatives such as polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfonated polyvinyl alcohol, and ethylene-modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, starch derivatives such as starch, oxidized starch, and etherified starch, and water-soluble polymers such as chitin, chitosan, casein, and gum arabic. These may be used alone or in combination of two or more. Among these, polyvinyl alcohol is preferred.

[0101] The amount of emulsifier added is not particularly limited, but is preferably, for example, about 1 to 10 parts by weight per 100 parts by weight of the solid content of the P3HA resin (B).

[0102] The method for producing aqueous dispersion (II) containing P3HA resin (B) is not particularly limited, but may involve first producing P3HA resin (B) within the cells of a microorganism, then disrupting the microbial cells in an aqueous dispersion state containing the P3HA resin (B). A precipitate is obtained by centrifugation from the aqueous dispersion of P3HA resin (B) obtained by disruption. This precipitate is washed with water and, if necessary, with methanol, and finally an appropriate amount of water is added to obtain aqueous dispersion (II) containing P3HA resin (B) with a desired solids concentration.

[0103] Alternatively, the microbial cells may be disrupted to obtain an aqueous dispersion of the P3HA resin (B), which may then be washed appropriately and spray-dried to obtain a powder of the P3HA resin (B), which may then be dispersed in water to obtain the aqueous dispersion (II). Alternatively, the P3HA resin (B) may be obtained in powder form and dispersed in water to obtain the aqueous dispersion (II).

[0104] The aqueous dispersion (II) described above is applied to the surface of the anchor layer to form a coating film. The application method is not particularly limited, and known methods can be used as appropriate. Specifically, spraying, scattering, slit coating, air knife coating, roll coating, bar coating, comma coating, blade coating, screen printing, gravure printing, etc. can be used.

[0105] After the coating film is formed, the coating film is heated and dried to form a resin layer. This drying step may be a step aimed solely at evaporating the aqueous medium contained in the aqueous dispersion (II), or may be a step aimed at fusing the particles of the P3HA resin (B) together to increase the uniformity of the resin layer, in addition to the evaporation.

[0106] When the drying step is intended solely to evaporate the aqueous medium, the heating temperature of the coating film in the drying step is not particularly limited, but may be a temperature lower than the melting point of the P3HA resin (B). Specifically, the upper limit of the heating temperature may be less than 130°C and may be 125°C or lower. The lower limit of the heating temperature is not particularly limited, but may be, for example, 70°C or higher, preferably 90°C or higher, and more preferably 100°C or higher. The heating time is not particularly limited, but may be, for example, 10 seconds to 10 minutes, and preferably 30 seconds to 5 minutes.

[0107] On the other hand, if the drying step is intended to evaporate the aqueous medium and fuse the P3HA resin (B) particles together, the heating temperature of the coating film in the drying step is preferably equal to or higher than the melting point of the P3HA resin (B). Heating at such a temperature melts at least a portion of the P3HA resin (B), and the molten portion cools and solidifies after heating, fusing the resin particles together and integrating the resin components, resulting in the formation of a more uniform resin layer. This improves the adhesion of the resin layer to the paper substrate layer and anchor layer, as well as the water and oil resistance of the resin layer.

[0108] The heating temperature is preferably 10 to 40°C higher than the melting point of the P3HA resin (B), and more preferably 20 to 30°C higher. Specifically, the heating temperature is preferably 160°C or higher, more preferably 165°C or higher, and particularly preferably 170°C or higher. The heating temperature is also preferably 200°C or lower. A heating temperature of 200°C or lower can avoid excessive drying of the paper substrate and thermal decomposition of the P3HA resin (B). The heating time is not particularly limited, but may be, for example, 10 seconds to 10 minutes, and preferably 30 seconds to 5 minutes. The melting point of the P3HA resin (B) refers to the highest peak top temperature in the crystal melting curve in differential scanning calorimetry.

[0109] This drying step can be carried out using a known heating method, such as hot air heating, infrared heating, ultrasonic irradiation, microwave heating, roll heating, or hot plate heating, which can be used alone or in combination of two or more.

[0110] After the drying step, a humidity control step may be carried out to adjust the moisture content of the dried paper base layer.

[0111] [Formation of resin layer by lamination method] In the embodiment in which the resin layer is formed by lamination, extrusion lamination or thermal lamination can be used. The extrusion lamination method may be a general extrusion lamination method. Specifically, a molten resin material (i.e., a resin composition containing the P3HA resin (B)) is extruded into a film form through a T-die, and is pressed onto the surface of the anchor layer while being cooled using a cooling roll. Immediately thereafter, the resin material is peeled off from the cooling roll to form a resin layer, thereby producing a laminate.

[0112] The thermal lamination method can be a general thermal lamination method. Specifically, first, a molten resin material (i.e., a resin composition containing the P3HA-based resin (B)) is extruded, for example, through a T-shaped die, and cooled using a cooling roll to form a film containing the resin material. Next, the obtained film is pressed onto the surface of the anchor layer using a heated roll or the like, to produce a molded product.

[0113] For the purpose of improving the adhesion between the resin layer and the paper substrate layer on which the anchor layer is formed, the surface of the anchor layer may be subjected to corona treatment, flame treatment, ozone treatment, or the like.

[0114] [Molded body] The molded article according to one aspect of the present embodiment includes the laminate described above and has a desired size and shape. The molded article is advantageous in a variety of applications because it is formed from a laminate including a resin layer containing a P3HA-based resin (B).

[0115] The molded article is not particularly limited as long as it contains the laminate, and examples thereof include paper, film, sheet, tube, plate, rod, container (for example, bottle container), bag, and part.

[0116] The molded article may be the laminate itself, or may be a product of secondary processing of the laminate. By subjecting the laminate to secondary processing, the molded article can be suitably used as various packaging container materials such as shopping bags, various bags, food and confectionery packaging materials, cups, trays, cartons, etc. (in other words, in various fields such as food, cosmetics, electronics, medicine, and pharmaceuticals). Because the molded article contains a resin layer that has high adhesion to substrates and good heat resistance, it can be more suitably used as containers for holding liquids, particularly containers for hot contents, such as cups for food and beverages such as instant noodles, instant soup, and coffee, and trays for prepared meals, bento boxes, and microwaveable foods. Because the laminate has excellent water resistance and oil resistance, it can be suitably used as a packaging material for packaging food and beverages that contain water or oil.

[0117] The secondary processing can be carried out in the same manner as conventional resin-laminated paper or coated paper, i.e., using various bag-making machines, filling and packaging machines, etc. Processing can also be carried out using machines such as paper cup forming machines, punching machines, and box making machines. In these processing machines, known techniques can be used to bond the laminate, such as heat sealing, impulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and frame sealing.

[0118] The heat-sealing temperature of the laminate varies depending on the adhesion method, but when using, for example, a heating-type heat-sealing tester equipped with a seal bar, the resin temperature can usually be set to 180° C. or lower, preferably 170° C. or lower, and more preferably 160° C. or lower. The lower limit of the resin temperature is usually 100° C. or higher, preferably 110° C. or higher, and more preferably 120° C. or higher.

[0119] The heat-sealing pressure for the laminate varies depending on the bonding method, but when a heating-type heat-sealing tester equipped with a seal bar is used, it is usually 0.1 MPa or more, preferably 0.5 MPa or more, and the upper limit of the heat-sealing pressure is usually 1.0 MPa or less, preferably 0.75 MPa or less.

[0120] In order to improve the physical properties of the molded article, the molded article can be composited with another molded article made of a material different from the molded article (for example, fiber, thread, rope, woven fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, plate, rod, container, bag, part, foam, etc.). These materials are also preferably biodegradable.

[0121] The following items list preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] paper base layer, An anchor layer containing a polyester resin (A) having a glass transition temperature of more than 46°C and an acid value of 30 mgKOH / g or more; and A laminate comprising a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B), and each layer being laminated in this order. [Item 2] Item 2. The laminate according to item 1, wherein the polyester resin (A) is biodegradable. [Item 3] Item 3. The laminate according to item 1 or 2, wherein the anchor layer further comprises a poly(3-hydroxyalkanoate)-based resin (C). [Item 4] 4. The laminate according to any one of items 1 to 3, wherein the poly(3-hydroxyalkanoate) resin (B) contains poly(3-hydroxybutyrate) (b-1). [Item 5] Item 5. The laminate according to item 4, wherein the content of the poly(3-hydroxybutyrate) (b-1) is 12% by weight or more and 21% by weight or less, based on 100% by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin (B). [Item 6] 6. The laminate according to any one of items 1 to 5, wherein the poly(3-hydroxyalkanoate)-based resin (B) comprises a poly(3-hydroxybutyrate)-based copolymer (b-2) having a 3-hydroxybutyrate unit and another hydroxyalkanoate unit. [Item 7] Item 7. The laminate according to item 6, wherein the content of the other hydroxyalkanoate units is 10 mol% or more and less than 24 mol% of the total amount (100 mol%) of monomer units constituting the poly(3-hydroxybutyrate)-based copolymer (b-2). [Item 8] 8. The laminate according to any one of items 1 to 7, wherein the poly(3-hydroxyalkanoate) resin (B) has a weight average molecular weight (Mw) of 100,000 or more and less than 400,000. [Item 9] A step (i) of applying an aqueous liquid (I) containing a polyester resin (A) having a glass transition temperature of more than 46°C and an acid value of 30 mgKOH / g or more to the surface of a paper substrate and drying the aqueous liquid to form an anchor layer; and A method for producing a laminate, comprising the step (ii) of forming a resin layer containing a poly(3-hydroxyalkanoate) resin (B) on the surface of the anchor layer. [Item 10] Item 10. The method for producing a laminate according to Item 9, wherein the step (ii) is a step of applying an aqueous dispersion (II) containing the poly(3-hydroxyalkanoate) resin (B) to a surface of the anchor layer and drying the applied dispersion to form the resin layer. [Item 11] Item 10. The method for producing a laminate according to Item 9, wherein the step (ii) is a step of forming the resin layer on the surface of the anchor layer by a lamination method using a resin composition containing the poly(3-hydroxyalkanoate)-based resin (B). [Example]

[0122] The present invention will be explained in more detail below with reference to examples and comparative examples, but the technical scope of the present invention is not limited to these examples.

[0123] The substances used in the examples and comparative examples are shown below. P3HB3HH-11: P3HB3HH (average content ratio of 3HB / 3HH=89 / 11 (mol % / mol %), weight average molecular weight of 260,000 g / mol) was produced according to the method described in WO 2008 / 010296. PHB: Poly(3-hydroxybutyrate)

[0124] (Method of manufacturing aqueous dispersion HB-1) P3HB3HH-11 and PHB were blended as P3HA-based resins in a ratio of 86.5 parts by weight of P3HB3HH-11:13.5 parts by weight of P3HB3HH-11:PHB. 3 parts by weight of partially saponified polyvinyl alcohol (Poval L508W, manufactured by Kuraray) was added as a water-soluble polymeric dispersant to 100 parts by weight of the resulting blend, and the mixture was stirred to obtain aqueous dispersion HB-1, which had a solids concentration of 40% by weight, consisting of P3HB3HH, PHB, and dispersant.

[0125] Example 1 Weight 50g / m 2 For one side of kraft paper (Oji Materia / bleached kraft paper, whale), the resin weight after drying is 1g / m 2 A water-based polyester resin coating solution AC-1 (biodegradable water-based polyester resin coating agent, GX-1473, manufactured by GOO Chemical Co., Ltd., solids concentration 25 wt%, glass transition temperature (Tg) 49°C, acid value 50-70 (mgKOH / g)) was applied using a bar coater so that the paper was coated with an anchor layer. The paper was then heated for 2 minutes in a hot air oven set at 100°C to form an anchor layer. The irreversible thermolabel (3E-80 manufactured by NOF Giken Kogyo Co., Ltd.) attached to the paper (coated surface) showed a temperature of 90°C. Next, on the anchor layer, a resin weight of 15 g / m after drying is applied. 2 After applying the aqueous dispersion HB-1 using a bar coater so that the resin layer was formed, the laminate was heated for 2 minutes in a hot air oven set at 180°C to obtain a resin layer. The irreversible thermolabel (5E-170 manufactured by NOF Corp.) attached to the upper end of the anchor layer showed a temperature of 170°C (corresponding to the surface temperature of the coating film). The resulting laminate was evaluated for oil resistance and interlayer adhesion, and the results are shown in Table 1.

[0126] (Examples 2 and 3) Laminates were obtained in the same manner as in Example 1, except that the resin basis weight of the anchor layer after drying was changed as shown in Table 1. The oil resistance and interlayer adhesion of the obtained laminates were evaluated. The results are shown in Table 1.

[0127] Example 4 The aqueous polyester resin coating solution AC-1 used in Examples 1 to 3 was mixed with the aqueous dispersion HB-1 in a solids ratio of AC-1:HB-1 = 95 parts by weight:5 parts by weight and stirred to prepare aqueous polyester resin coating solution AC-2 (solids concentration 25%). Except for forming the anchor layer using this coating solution AC-2, the same procedure as in Example 3 was repeated to obtain a laminate, and the oil resistance and interlayer adhesion of the obtained laminate were evaluated. The results are shown in Table 1.

[0128] Example 5 The aqueous polyester resin coating solution AC-1 used in Examples 1 to 3 was mixed with the aqueous dispersion HB-1 in a solids ratio of AC-1:HB-1 = 85 parts by weight:15 parts by weight and stirred to prepare the aqueous polyester resin coating solution AC-3 (solids concentration 25%). Except for forming the anchor layer using this coating solution AC-3, the same procedure as in Example 3 was repeated to obtain a laminate, and the oil resistance and interlayer adhesion of the obtained laminate were evaluated. The results are shown in Table 1.

[0129] Example 6 P3HB3HH-11 was melt-kneaded and extruded into strands using a twin-screw extruder at a set temperature of 151°C and a screw rotation speed of 100 rpm, and the strands were then passed through hot water at 40°C to solidify them and cut into pellets. The resulting pellets were fed into a single-screw extruder equipped with a T-die, extruded, taken up with a cooling roll set at 60°C, and laminated to a thickness of 30 μm on the surface of the anchor layer prepared in Example 3 to obtain a laminate. The oil resistance and interlayer adhesion of the resulting laminate were evaluated. The results are shown in Table 1.

[0130] (Comparative Example 1) A laminate was obtained in the same manner as in Example 3, except that the anchor layer was formed using aqueous polyester resin coating solution AC-4 (biodegradable aqueous polyester resin coating agent, GX-1471, manufactured by GOO Chemical Co., Ltd., solids concentration 25 wt%, glass transition temperature (Tg) 48°C, acid value less than 10 (mgKOH / g)). The oil resistance and interlayer adhesion of the obtained laminate were evaluated. The results are shown in Table 1.

[0131] (Comparative Example 2) A laminate was obtained in the same manner as in Example 2, except that the anchor layer was formed using aqueous polyester resin coating solution AC-5 (Pluscoat, Z-221, manufactured by GOO Chemical Co., Ltd., solids concentration 20 wt %, glass transition temperature (Tg) 47°C, acid value less than 5 (mgKOH / g)). The oil resistance and interlayer adhesion of the obtained laminate were evaluated. The results are shown in Table 1. Z-221 is a polyester resin used in Comparative Example 1 of Patent Document 1.

[0132] (Comparative Example 3) A laminate was obtained in the same manner as in Example 2, except that the anchor layer was formed using aqueous polyester resin coating solution AC-6 (Pluscoat, RZ-105, manufactured by GOO Chemical Co., Ltd., solids concentration 25 wt %, glass transition temperature (Tg) 52°C, acid value less than 5 (mgKOH / g)). The oil resistance and interlayer adhesion of the obtained laminate were evaluated. The results are shown in Table 1. RZ-105 is a polyester resin used in Comparative Example 2 of Patent Document 1.

[0133] (Method for measuring basis weight) The laminate obtained in each example and comparative example was cut into a piece measuring 10 cm x 10 cm, and its weight was measured. The weight was then subtracted from the weight obtained by subtracting the weight of the paper substrate and multiplied by 100 to obtain the basis weight (dry weight per unit area of ​​the resin layer or anchor layer).

[0134] (Evaluation method for oil resistance) Ageless Seal Check Liquid (manufactured by Mitsubishi Gas Chemical Company) was sprayed onto any two A4-sized points on the surface of the resin layer of the laminate, and then 120 seconds later, the presence or absence of any infiltrated areas was confirmed when viewed from the back of the sprayed surface. The oil resistance of the two tested samples was evaluated according to the following criteria: If the evaluation was ◯ or △, it was determined that there was no problem in practical use. <Evaluation criteria> 〇: Ageless Check liquid does not penetrate to the back side at all △: The Ageless Check liquid did not penetrate to the backside, but bleeding was observed in part of the resin layer. ×: Ageless Check liquid has penetrated to the backside in one or more places

[0135] (Method for evaluating interlayer adhesion) In order to evaluate the interlayer adhesion of the obtained laminate, the adhesiveness after heat sealing was evaluated. First, two square test pieces of 25 mm × 40 mm were cut out from the obtained laminate, and the resin layers were brought into contact with each other, and the heat seal area was 25 mm × 20 mm, the pressure temperature was 130 ° C, and the pressure was 1.5 kgf / cm 2 The heat sealing was carried out with a pressure application time of 0.5 seconds. To measure the heat seal strength of the prepared heat seal paper test pieces, an autograph was used, and the peeled portion was visually observed after 180° peeling. The heat seal adhesiveness was evaluated according to the following criteria. If the evaluation was good or fair, it was judged to be satisfactory for practical use. [Evaluation criteria] ○: Peeling occurs within the paper substrate (paper substrate is destroyed). △: Most of the peeling occurs within the paper substrate (paper substrate is destroyed). ×: Peeling occurs between the resin layers.

[0136] [Table 1]

[0137] 〔result〕 Table 1 shows that the laminates of Examples 1 to 6, which have anchor layers containing polyester resin (A) with a glass transition temperature of over 46°C and an acid value of 30 mgKOH / g or more, had good interlayer adhesion and also good oil resistance. On the other hand, the laminates of Comparative Examples 1 to 3, in which the anchor layer was formed using a polyester resin with an acid value of less than 30 mgKOH / g, although the glass transition temperature was above 46° C., had insufficient interlayer adhesion.

Claims

1. paper base layer, An anchor layer containing a polyester resin (A) having a glass transition temperature of more than 46°C and an acid value of 30 mgKOH / g or more; and A laminate comprising a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B), and each layer being laminated in this order.

2. The laminate according to claim 1 , wherein the polyester resin (A) is biodegradable.

3. The laminate according to claim 1 or 2, wherein the anchor layer further comprises a poly(3-hydroxyalkanoate)-based resin (C).

4. The laminate according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate)-based resin (B) contains poly(3-hydroxybutyrate) (b-1).

5. 5. The laminate according to claim 4, wherein the content of the poly(3-hydroxybutyrate) (b-1) is 12% by weight or more and 21% by weight or less, based on 100% by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin (B).

6. The laminate according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate)-based resin (B) comprises a poly(3-hydroxybutyrate)-based copolymer (b-2) having a 3-hydroxybutyrate unit and another hydroxyalkanoate unit.

7. The laminate according to claim 6, wherein the content of the other hydroxyalkanoate units is 10 mol% or more and less than 24 mol% of the total amount (100 mol%) of monomer units constituting the poly(3-hydroxybutyrate)-based copolymer (b-2).

8. 3. The laminate according to claim 1, wherein the poly(3-hydroxyalkanoate) resin (B) has a weight average molecular weight (Mw) of 100,000 or more and less than 400,000.

9. A step (i) of applying an aqueous liquid (I) containing a polyester resin (A) having a glass transition temperature of more than 46°C and an acid value of 30 mgKOH / g or more to the surface of a paper substrate and drying the aqueous liquid to form an anchor layer; and A method for producing a laminate, comprising: a step (ii) of forming a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B) on the surface of the anchor layer.

10. The method for producing a laminate according to claim 9, wherein the step (ii) is a step of applying an aqueous dispersion (II) containing the poly(3-hydroxyalkanoate)-based resin (B) to a surface of the anchor layer and drying the applied dispersion to form the resin layer.

11. The method for producing a laminate according to claim 9, wherein the step (ii) is a step of forming the resin layer on a surface of the anchor layer by a lamination method using a resin composition containing the poly(3-hydroxyalkanoate)-based resin (B).

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